# United States v. Leon > Supreme Court of the United States · September 18, 1984 · 468 U.S. 897 URL: https://www.frixlaw.com/law-library/cases/9429767 ## Case - **Full name:** UNITED STATES v. LEON Et Al. - **Court:** Supreme Court of the United States - **Decided:** September 18, 1984 - **Citations:** 468 U.S. 897; 104 S. Ct. 3405; 82 L. Ed. 2d 677; 1984 U.S. LEXIS 153 - **Precedential status:** Published - **Opinion:** Concurrence by Blackmun - **Judges:** Blackmun, Brennan, Burger, Powell, Rehnquist, Stevens, White - **Cited by:** 7,837 later opinions in the Frix Law Library ## Citator (automated) - **Yellow flag:** Criticized by State v. Marsala, 216 Conn. 150 (1990). - Negative treatments: 6 - Distinguished by: 56 - Full citator and citing cases: https://www.frixlaw.com/law-library/cases/9429767 ## How later opinions describe it (automated extraction) - holding that the exclusionary rule should not be applied to bar the use of evidence obtained by officers acting in reasonable reliance on a search warrant issued by a detached and neutral magistrate but ultimately found to be invalid, and stating that whether to apply the rule… - holding that the magistrate may believe that evidence of a crime will be exclusionary rule should not be used to suppress evidence found.” Allen, 211 F.3d at 975 . However, here, as noted by when the officers who obtained the evidence acted in the federal magistrate judge in h… - explaining that, because the “purpose of the exclusionary rule is to deter unlawful police conduct,” excluding evidence obtained pursuant to a warrant will not further the ends of the exclusionary rule in situations where the offer’s conduct was objectively reasonable — situat… - stating exclusion could still be warranted if: (1) the warrant was based on an affidavit “so lacking in indicia of probable cause as to render official belief in its existence entirely unreasonable;” or (2) the warrant was “so facially deficient—i.e., in failing to particulari… - stating that the Court had not yet recognized any form of good-faith exception to the Fourth Amendment exclusionary rule but that its "evaluation of the costs and benefits of suppressing reliable physical evidence seized by officers reasonably relying on a warrant issued by a … ## Opinion text *927 Justice Blackmun, concurring. The Court today holds that evidence obtained in violation of the Fourth Amendment by officers acting in objectively reasonable reliance on a search warrant issued by a neutral and detached magistrate need not be excluded, as a matter of federal law, from the case in chief of federal and state criminal prosecutions. In so doing, the Court writes another chapter in the volume of Fourth Amendment law opened by Weeks v. United States, 232 U. S. 383 (1914). I join the Court’s opinion in this case and the one in Massachusetts v. Sheppard, post, p. 981, because I believe that the rule announced today advances the legitimate interests of the criminal justice system without sacrificing the individual rights protected by the Fourth Amendment. I write separately, however, to underscore what I regard as the unavoidably provisional nature of today’s decisions. As the Court’s opinion in this case makes clear, the Court has narrowed the scope of the exclusionary rule because of an empirical judgment that the rule has little appreciable effect in cases where officers act in objectively reasonable reliance on search warrants. See ante, at 918-921. Because I share the view that the exclusionary rule is not a constitutionally compelled corollary of the Fourth Amendment itself, see ante, at 905-906, I see no way to avoid making an empirical judgment of this sort, and I am satisfied that the Court has made the correct one on the information before it. Like all courts, we face institutional limitations on our ability to gather information about “legislative facts,” and the exclusionary rule itself has exacerbated the shortage of hard data concerning the behavior of police officers in the absence of such a rule. See United States v. Janis, 428 U. S. 433, 448-453 (1976). Nonetheless, we cannot escape the responsibility to decide the question before us, however imperfect our information may be, and I am prepared to join the Court on the information now at hand. *928 What must be stressed, however, is that any empirical judgment about the effect of the exclusionary rule in a particular class of cases necessarily is a provisional one. By their very nature, the assumptions on which we proceed today cannot be cast in stone. To the contrary, they now will be tested in the real world of state and federal law enforcement, and this Court will attend to the results. If it should emerge from experience that, contrary to our expectations, the good-faith exception to the exclusionary rule results in a material change in police compliance with the Fourth Amendment, we shall have to reconsider what we have undertaken here. The logic of a decision that rests on untested predictions about police conduct demands no less. If a single principle may be drawn from this Court’s exclusionary rule decisions, from Weeks through Mapp v. Ohio, 367 U. S. 643 (1961), to the decisions handed down today, it is that the scope of the exclusionary rule is subject to change in light of changing judicial understanding about the effects of the rule outside the confines of the courtroom. It is incumbent on the Nation’s law enforcement officers, who must continue to observe the Fourth Amendment in the wake of today’s decisions, to recognize the double-edged nature of that principle. --- Source: Frix Law Library, https://www.frixlaw.com/law-library/cases/9429767. Public record. Not legal advice.